New approach to total energy management

Electronics can be controlled with dc/dc converters that control several aspects of their sub-power delivery system on the fly

BY ALAN ELBANHAWY
Akros Silicon Inc.
www.akrossilicon.com

The role of power management ICs in electronic equipment is rapidly being eclipsed by the demand for energy management. Advance IC topologies are now available that offer designers tremendous flexibility while simplifying the daunting task of managing system energy consumption under real-time operating conditions.

This article describes a new approach to energy management in electronic devices through use of dc/dc converters with the ability to control several aspects of their sub-power delivery system on the fly. It will also show how implementation of a multi-rail power management IC, through digital interface, provides an efficient and effective means of managing features like sequencing, multi-rail on/off, voltage margining, measuring input and output power and EMI management through sophisticated spread-spectrum clocking.

Total energy mgmt vs. power mgmt

Designing power delivery subsystems for modern electronic devices necessitates multiple converters to deliver the myriad of rails needed for the device and the availability of advanced control features in these converters. The specifics of these features and capabilities are evolving as the complexity and sophistication of these devices moves into new realms of satisfying the unlimited appetite of consumers for data.

Modern power designers demand flexibility from power ICs that allow them to have robust and reliable system designs and the ease of implementation leading to successful products with good time-to-market. Gone are the days of selecting from a finite list of basic ‘jelly-bean’ general purpose IC widgets. We are now in a time where power products are differentiating themselves by the sophistication of architecture and a long list of enabling features that ultimately renders the optimum power systems, meets the extremely demanding design specifications in the smallest conceivable footprints, and satisfies a cost of the bill of materials (BOM) that was unimaginable only few years ago.

Power management, that is, the operation and control of multiple voltages typically required in an electronic system, is no longer sufficient. Total energy management requires attention to the dynamic details of the system to affect optimum energy usage. Must-have features for total energy management include:

• Control mode flexibility allowing for continuous control mode (CCM) and discontinuous control mode (DCM) coupled with sleep mode for maximum energy conservation under varying conditions from full load, to low load to no load.

• Flexible sequencing control to optimize multiple-rail output power start-up

• Programmable frequency operation to permit optimization of power consumption / board space trade-offs

• Voltage margining to manage power consumption

• Real-time rail enable/disable to power functions only when required

• High-efficiency EMI control and mitigation

An example of the total energy management philosophy is Akros Silicon’s new AS19xx family of high efficiency green dc/dc converters. Each of Power Managers (PM) integrates multiple features into each device (see Fig. 1).The product family comprises 10 products with five different functionalities. All are pin and PCB compatible and come in either hardware or software (I2C interface) versions. Each has three or two outputs as a combination of two fully integrated synchronous dc/dc converters and one versatile controller configurable as buck, boost or LED drive.

This solution was developed to meet the designer’s energy management needs without adding complication, space and cost, and all while providing real-time power monitoring and energy management features that increase efficiency. The idea behind this product family is to offer designers a choice of selectable ICs that can be used in a wide range of applications and across a multitude of platforms.

Fig. 1. Pin and software (I2C) compatible dc/dc converters in the AS19xx family offer real-time energy management.

Total energy management is applicable to a wide range of applications, including 4G LTE residential gateways and femtocells to tablets and large display-oriented consumer devices, ultra-books, e-books, digital photo frames, NAS and media hubs, Internet-TV and IPTV set-top boxes, automotive infotainment systems, solid-state lighting, and communication equipment with cluster-power or intermediate bus architectures, as well as many other applications.

Here are a few examples of how this integrated approach facilitates the design and improves operational performance and efficiency:

Dynamic LED backlight control

A tablet PC’s LED backlight screen consumes 50% of its power. Designers applying AS19xx devices can achieve PWM dimming using an external PWM or internal I2C-based and 32-step (5-bit) logarithmic dimming. In this application the internal I2C software can dim the screen based on content, such as when watching a movie as opposed to reading content. (see Fig. 2 )

Fig. 2: The AS19xx enables multiple-load LED dimming options.

Dynamic power amplifier control

4G LTE Gateways/Cells require the power amplifier (PA) to be operational only during the transmit mode. By employing dynamic, high-speed control, the PA power can be disabled during the listing mode, thus eliminating energy waste (see Fig. 3). The AS19xx devices can enable/disable each rail in 10 µs – fast enough to permit this function without external control.

Fig. 3: 4G data link transfers only require PA on during transmit period.

Real-time input power measurements

During the development phase of an electronic system, changes in the software can have dramatic effects on power consumption. Total energy management devices, like the AS19xx, are capable of providing feedback on power usage on each rail in real time. This can speed development and result in more efficient product designs.

EMI management

Switch-mode power supplies require EMI filtering to minimize the injection of power supply noise onto the power line. Using spread-spectrum clocking, which is integrated in AS19xx devices, mitigates EMI and leads to less design cost and higher system efficiency.

The insatiable appetite for power and multiple rails in modern electronics is only matched by the need for high performance and advanced operational and control features that confronts power system designers. Their major challenge is to achieve all the design requirements with an implementation that has the highest efficiency (≥95%), occupies the smallest possible PCB real estate and at a cost sometimes bordering on the impossible. In other words, IC designers have to become system designers who use the available data to make energy management choices for their applications. The most critical question they must consider is: Which IC(s) will do the job? A total energy management approach embodied in the AS19xx dc/dc converter family offers a simple, elegant answer. This family of 10 products with selectable and integrated features was developed to replace pure power management with the new approach of total energy management. ■